1. Field of the Invention
This invention relates to an electrical contact system particularly useful in printed circuit board applications. More particularly, this invention relates to a socket contact structure which allows for increased durability and reliability over many contact cycles, decreased centerline spacing to accommodate high density connectivity requirements, and improved socket-to-pin contact.
2. Related Prior Art
Electrical connectors utilizing pin-receiving sockets are widely used in the electronics industry for electrically connecting circuit members. Socket-to-pin contacts are used in printed circuit board applications that require robust, high density connectors.
A continuing objective of the electronics industry has been to make smaller, stronger, more reliable and more durable electrical connectors. Durability of a connector is measured in terms of contact cycles. The contact area of a socket must be capable of withstanding the forces produced by repeated insertions of a contact pin. Additionally, high density pin arrangements require narrow centerline spacing between adjacent pins. Socket contacts must accommodate high density pin arrays without loss in strength or durability. The prior art discloses a variety of socket contact structures as shown in FIG. 1. Socket contacts typically use elongated spring tines to receive and engage the outer periphery of cylindrical pin contacts. U.S. Pat. No. 4,734,064 entitled "Electrical Socket Contact With Convex Engaging Tines", issued Mar. 29, 1988 to Knapp et al., is an example of a "tulip-shaped" socket contact. This socket contact is depicted in FIG. 1a. Cantilevered tines A are bent to form a tulip-shaped entry for receiving contact pins with the convex portion B of each tine engaging the pin contact. Although convex tines reduce wear on contact pins and assist in pin alignment, they are difficult to manufacture.
U.S. Pat. No. 4,379,611 entitled "Connector With Low Force Socket Contact Having An Integral Hood", issued Apr. 12, 9183 to Foege et al., similarly discloses a connector receptacle with cantilevered tines bent into a convex shaped at their pin-receiving ends. The tines are not initially angled inward and pose manufacturing problems similar to those presented by the Knapp disclosure.
The prior art also discloses socket contacts using both "box-shaped" and "U-shaped" pin receptacles. U.S. Pat. No. 4,874,338 entitled "Receptacle Box Terminal With Improved Contact Area", issued Oct. 17, 1989 to Bakermans, is an example of a box-shaped pin receptacle. This socket contact structure is depicted in FIG. 1b. Each beam C of the receptacle box is embossed with a contact "dimple" D to engage a contact pin. The beams are not cantilevered.
U.S. Pat. No. 4,907,990 entitled "Elastically Supported Dual Cantilever Beam Pin-Receiving Electrical Contact", issued Mar. 13, 1990 to Bertho et al., is an example of a U-shaped pin receptacle. This socket contact structure is depicted in FIG. 1c, The cantilever beams E are bent at their free ends in a convex shape to engage the pin contact. U.S. Pat. No. 4,750,889 also discloses a U-shaped receptacle having a cantilevered arms each having a contact point formed by a bend in the tip of the arms. The cantilevered arms are not initially angled inward.
The prior art discloses various techniques for forming constant and distinct contact points between the socket and inserted contact pin. Typically this is accomplished by either using embossed contact domes or "dimples", or by bending cantilever arms at the pin receiving ends. French patent 960,968 discloses an electrical contact having three sides, all of which have spherical contact dimples at the pin-receiving ends. U.S. Pat. No. 4,383,724 similarly discloses an electrical contact utilizing contact dimples. However, the prior art does not disclose cantilevered tines embossed with contact dimples.
Other designs disclose contact points formed by bending the tips of cantilevered arms. Variations of this technique have been suggested as evidenced by those disclosed in U.S. Pat. Nos. 4,232,931; 4,466,684; 4,473,269; and 4,529,260. This prior art does not discloses the use of contact dimples.
In order to remedy the deficiencies of the prior art, it is an object of the present invention to provide an electrical socket contact which is easily manufactured, highly durable and reliable. It is also an object of this invention to provide an electrical socket contact which permits tight centerline spacing of electrical components, decreased contact cavity size, and constant pin insertion force. In accordance with this and other objects, the present invention teaches the use of a combination of dimpled cantilever opposed beams initially angled inward to provide a torsional and compressional normal force on an inserted contact pin.